Automatic control and thread cutter for sewing machines

ABSTRACT

The present attachment for sewing machines automatically positions the needle, raises and lowers the pressure foot, properly tensions the sewing thread, and severs said sewing thread and includes a control for starting, speeding up, slowing down, or stopping the operation of the sewing machine. The attachment also permits the operator thereof to put a plurality of stitches or single stitch at a time into the workpiece before automatically severing the thread therefrom and also provides means for automatically positioning the needle in its top position or lowermost position as well as means for stopping the sewing machine when the needle is in its up position opening said positioning means so that the operator can down-position the needle and lift the pressure foot for turning the workpiece around the needle.

United States Patent [72] Inventors RobertF. Miller Camp Hill;

Roy E. Miller, Mechanicsburg, both of Pa. [21] Appl. No. 856,967 [22] Filed Sept. 11, 1969 [23] Division of Ser. No. 725,529, Apr. 19,

1968, Pat. No. 3,528,379, which is a continuation-in-part of Ser. No. 432,721, Feb. 15, 1965, al3and oned.

45' Patented 0&3, 1971 [73] Assignee The Reece Corporation Waltham, Mass.

[54] AUTOMATIC CONTROL AND THREAD CUTTER Primary Examiner-James R. Boler Att0rneyLinton & Linton ABSTRACT: The present attachment for sewing machines automatically positions the needle, raises and lowers the pressure foot, properly tensions the sewing thread, and severs said sewing thread and includes a control for starting, speeding up, slowing down, or stopping the operation of the sewing machine. The attachment also permits the operator thereof to put a plurality of stitches or single stitch at a time into the workpiece before automatically severing the thread therefrom and also provides means for automatically positioning the needle in its top position or lowermost position as well as means for stopping the sewing machine when the needle is in its up position opening said positioning means so that the operator can down-position the needle and lift the pressure foot for turning the workpiece around the needle.

PATENTED um 5|97l 3,610,188

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ATTORNEYS.

AUTOMATIC CONTROL AND THREAD CUTTER FOR SEWING MACHINES This application is a division of applicants copending application Ser. No. 725,579, filed Apr. 19, 1968, now U.S. Pat. No. 3,528,379, which was a continuation-in-part of applicants application Ser. No. 432,721, filed Feb. 15, 1965, now abandoned.

The present invention is concerned with an improvement in sewing machines and more particularly is directed to apparatus for automatically controlling the operation of the sewing machine and severing the sewing thread.

The principal object of the present invention is to provide apparatus attachable to conventional sewing machines which apparatus while under the control of an operator, will automatically position the needle, raise and lower the presser foot, properly tension the sewing thread, and sever said sewing thread and including a control for starting, speeding up, slowing down or stopping the operation of the sewing machine.

A further important object of the invention is to provide means for modifying conventional sewing machines by the addition of reliable equipment which results in faster and simpler sewing operations and automatically positions the sewing needle and cuts the thread giving the operator the choice of putting many stitches or one single stitch in at a time into the workpiece before automatically severing the thread therefrom.

Another important object is to provide means for automatically positioning the needle bar with the needle at its top position or at its lowermost position and with means for stopping the sewing machine when the needle is in its up position breaking an electrical circuit connected to said positioning means whereupon the operator can energize said electrical circuit for down-positioning said needle bar and lifting the presser foot allowing the operator to turn the workpiece around the needle.

A further object of the invention is to provide means for automatically and properly cutting the sewing thread between the thread-handling system and the workpiece when each sewing step of the workpiece is completed.

Further objects of the invention will be in part obvious and in part pointed out in the following detailed description of the accompanying drawings in which:

FIG. 1 is a front perspective view of a conventional sewing machine with the apparatus of the present invention connected thereto.

FIG. 2 is an enlarged perspective view of the needle bar carrying end of a sewing machine arm modified according to the present invention.

FIG. 3 is an enlarged front elevation of a part of a sewing machine in accordance with the present invention with elements removed to show the sewing machine drive.

FIG. 4 is an end view taken from the right of FIG. 3.

FIG. 5 is an enlarged sectional view taken on line 5-5 of FIG. 3.

FIG. 6 is a cross-sectional view taken on line 66 of FIG. 3 and laterally of the sewing machine bed showing the positioning cylinder of the present apparatus.

FIG. 7 is a greatly enlarged detail view of the needle-positioning control with its cap removed.

FIG. 7ais an exploded perspective view of the synchronizer valve bracket and roller and handwheel.

FIG. 8 is a greatly enlarged cross-sectional view taken on line 8-8 of FIG. 6.

FIG. 9 is an end view of the slip clutch partially shown in FIG. 8.

FIG. 10 is an enlarged top view of the sewing thread cutoff.

FIG. 11 is a cross-sectional view taken on line 11-11 of FIG. 10.

FIG. 12 is a cross-sectional view taken on line 12-12 of FIG. 11.

FIG. 12a is an end view of the thread cutoff tubes.

FIG. 13 is a greatly enlarged sectional view taken on line 13-13 of FIG. 2.

FIG. 14 is a schematic diagram of the pneumatic and electrical system of the present apparatus.

FIG. 15 is a partial cross-sectional view taken on line 15- 15 of FIG. 4 showing the rear of the sewing machine and the presser foot controls.

FIG. 16 is a wiring diagram of the apparatus when the needle is up and presser foot raised.

FIG. 17 is a wiring diagram of the apparatus when the needle is down.

And FIG. 18 is an enlarged view of the knee switch forming part of the present apparatus.

Referring now more particularly to the accompanying drawings in which like and corresponding parts are designated by similar reference characters, LA and LB designate right and standard legs and LC and LD the left-hand standard legs. E is a rod extending between and connected to said standards with a treadle F having a tube G rotatably mounted on rod E. H is a sewing machine bed supported by said standards while I is an upright mounted on said bed and having crossarm J supporting rod K on which is rotatably mounted a spool L of thread M. Guide arm N is also mounted on upright I and has eye 0 through which thread M passes to pin P on the cantilever arm R of a conventional sewing machine generally designated Q. Said sewing machine slideably supports needle bar S with needle T and presser foot U.

Said sewing machine has a drive shaft handwheel V around which extends drive belt W. X is the bedplate of the sewing machine and AA a bobbin.

The above elements A to AA inclusive are conventional structures for sewing machines and supporting structure therefor.

Link 1 is pivotally connected at one end to bearing 2 carried by treadle F and pivotally connected by stub axle 3 to one end of a second link 4.

Link 4 has an arm 5 fixedly connected thereto and a bent end 6 while arm 5 is pivotally connected by pin 7 to the piston rod 8 of a pneumatic brake cylinder 9 to which is attached a solenoid valve 10. Arm 1! is fixedly connected at one end to brake cylinder 9 and pivotally connected by pins 13 to the control yoke 13a of a combination electric motor, clutch and brake l4. Said electric motor, clutch and brake 14 may, for example, be a Singer Electric Transmitter" series 552 or 553 produced by The Singer Manufacturing Company, Elizabethport F, New Jersey.

Said motor, clutch and brake l4 hereinafter referred to as a transmitter, is adjustably fastened to the bottom of bed H by any conventional means such as bolts or the like (not shown). A finger 12 fixedly mounted on said member 14 pivotally supports arm 11 and the other bent end of link 4 by means of a stub axle 12a.

Said transmitter 14 has a slideable drive shaft extending therefrom through control yoke 13a pivotally connected by pins 13 to arm 11. Axial movement of yoke 13a axially moves drive shaft 14a due to stops (not shown) on said drive shaft for engaging or disengaging said drive shaft through a mechanism (not shown) in transmitter 14 with the electric motor through the clutch or brake in transmitter 14. v

A pulley 15 is fixedly connected to shaft 14a as is a second pulley 16. Drivebelt W extends around pulley 15 while drivebelt 17 extends around pulley 16.

A plate 18 is fixedly connected to bed H and extends normal thereto. Said plate has a slot 19 through which is adjustably mounted the shaft 20a rotatably supporting a pulley 20 by means of a nut (not shown) on said pulley shaft on the opposite side of plate 18 to said pulley 16. Further pulleys 21 and 210 are rotatably mounted on plate 18.

Piston rod 23 of pneumatic cylinder 24 has screws 22 around which the ends of belt 17 are fastened while said belt extends around pulleys 20,21 and 21a. Cylinder 24 has tubes 25 and 26 connected to the ends thereof for the operation of said piston rod.

Brake cylinder 9 has tubes 26 and 27 connected to the ends thereof for the control of piston rod 8 while solenoid valve 10 has a tube 28 for the admission of air under pressure into the head of brake cylinder 9 as determined by solenoid valve 10.

A pneumatic speed control 29 has an air line tube 30 connected to the bottom thereof while the top is connected to a presser foot lift cylinder 31 operating a piston rod 31a whose connection to presser foot U will be explained hereinafter.

An angle rod 32 has a knee plate 34A attached thereto by clamp 34. Said angle rod is pivotally connected by stub axle 33 to transmitter 14 and is also fixedly connected by welding or the like to cylinder 31 for raising the same.

A microswitch MS 01 is fixedly mounted on transmitter 14 with its control positioned for being pushed by link 4 when the same is raised. A second microswitch MS 02 is carried by link 4 and has its control positioned for being pushed against member 14 when link 4 is raised.

A make and break electrical switch 35 for the electrical circuit is housed in box 36 attached to bed H.

A bobbin winder is shown at 37 in FIG. 4 bearing against belt W.

A cylindrical housing 38 has an extension V of the sewing machine drive shaft rotatably extending through an axial bore of said housing, while cam 39 therein is fixedly connected to said extension V' and thus to handwheel V for rotation therewith. Said cam is circular except for radial point 40. A rocker 41 of electrical insulating material is pivotally mounted on pin 42 carried by housing 38 and carries a spring contact 44. A point 45 is fixedly mounted on housing 38 for normally being engaged by contact 44 due to spring 43 connected to housing 38 and rocker 41.

A second insulating rocker 46 is pivotally mounted on pin 47 carried by housing 38 and said rocker 46 is held against cam 39 by spring 48 attached to said rocker and housing 38. Said rocker carries a spring contact 49 normally bearing against point 50 fixedly connected to housing 38.

Points 45 and 50 are positioned 180 apart and so that cam 39 opens one contact 44 or 49 from its respective point 45 or 50 when the needle bar S is all the way up and the other of said contacts when the needle bar is all the way down. A cable 51 is connected to points 45 and 50.

Pulley 16 contains a slip clutch provided by hub 16a keyed by key 54 in slot 55 to shaft 14a and positioned within axial bore 52 of said pulley. A plurality of rollers 53 are positioned between hub 16a and said pulley 16 and hub 160 has a series of spaced-apart radial teeth 56 and inwardly slanting curved peripheral portions 57 each extending between a pair of consecutive teeth 56 with a roller 53 positioned on each portion 57 for rolling movement between the pair of teeth 56 terminating said portion 57. A washer 58 is positioned against the outer end of said hub 16a and said pulley 16 while a ring nut 59 in threaded engagement with threads 60 on shaft 14a retains washer 58 in place. Hub 160 further has an annular flange 61 which provides a guide for the inner end of said pulley 16. Thus hub 16a, pulley 16, washer 58 and flange 61 provide a cage for rollers 53.

As best shown in FIGS. 2 and 5, the end face 62 of said sewing machine arm R has a recess 63 in which is mounted microswitch 64 alongside a pair of microswitches 65 and 65a. Microswitch 64 has an extended control bar 66 spaced from extended control bars 67 and 67a of microswitches 65 and 650, respectively.

A block 68 is fastened to the end of a piston rod 81 by screws 69 and has a lateral finger 70 extending between control bar 66 and control bars 67 and 67a.

Sewing machine arm end 62 has recesses 71 in the back, 72

.in the front and 73 in the bottom leading to recess 63 and a cover plate 74 in FIG. 4, for said arm end 62.

A U-shaped guide 75 is mounted on the front of arm end 62 while rollers 76, 77, and 78 extend across opening 72.

Pigtails 79 and 80 are connected to block 68 and positioned for extending through opening 72 between rollers 76, 77 and 78.

Said piston rod 81 extends through opening 71 into a pneumatic cylinder 82 fastened to the rear side of arm end 62 and which cylinder has a tube 82a connected to the inner end thereof, a screw 83 whose threads are in threaded engagement with cylinder 82 and lock nut 84b with screw 83 extending into cylinder 84 for limiting the movement of piston rod 81 towards the outer end of said cylinder. A coil spring 85 encircles piston rod 81 between block 68 and said cylinder.

A pin 86 attached to arm end 62 in opening 73 pivotally supports bent lever 87 extending through said opening 73. A sleeve 88 of a thread clamp is in threaded engagement with arm end 62 and has coil spring 89 on the inner end thereof while valve-shaped stem 90 slideably extends through said sleeve 88 and coil spring 89 with its flanged inner end against arm 87 and retaining coil spring 89 against sleeve 88. Said sleeve has a valve-seat-shaped recess 91 in the outer end thereof for at times receiving the outer end of valve stem 90.

A thread guide 93 attached to arm R has bent spring arms 92 adjustably held by bolt 94 in threaded engagement with said arm R.

An automatic thread tension release consists of a cylinder 95, a piston 95a in said cylinder, a threaded rod 95b fixedly connected at one end to arm R, a disc 95c slideably mounted on rod 95b, a second disc 95d fixedly connected to arm R, tube 96 connected to the outer end of cylinder 95, nut 97 in threaded engagement with rod 95b and a coil spring 98 surrounding rod 95b between said nut and the inturn end 95c of said cylinder 95. Rod 95b is split at its outer end for receiving pin 95F extending through a slot in the extension of said piston and into cylinder 95 for preventing the turning of said cylinder.

A thread cutoff is best shown in FIGS. 5 and 10 to 12a, inclusive. Said thread cutoff has a pair of superposed curved tubes 99 and 100 with a steel band 101 extending in tube 99 and a second steel band 102 extending in tube 100. Tube 99 has an upturned lip 103 at the free outer end thereof and an opening 104 extending therethrough above the free outer end of tube 100 and bobbin AA of the sewing machine 0. Said tube free ends are positioned just below the needle opening for bed X of the sewing machine.

A cylinder head 105 is positioned below a bottom portion 106 of the sewing machine in threaded engagement with a cylinder tube 108. A cylinder cap 107 also is in threaded engagement with cylinder tube 108, but positioned above bottom portion 106 of the sewing machine and has tubes 99 and 100 integral therewith and openings for bands 101 and 102 which bands are also integral with piston rod 109, slideable in tube 108 and extending through head 105. A coil spring 110 surrounds piston rod 109 between head 105 and not 111 in threaded engagement with said piston rod. A tube 112 is connected to and through head 105.

As shown in FIG. 10 the sewing machine bottom member 106 has a semicircular recess 116 while a block also has a semicircular recess 113 for holding tube 108 therebetween. Bolts 115a and 115k extend through block 115 and screw into bottom member 106 holding said block therein.

Microswitch 117, FIGS. 1 and 18, is mounted on standard leg LC with its control button 117a facing a knee plate 118 pivotally mounted on rod 119a pivotally connected by pivot 119 to bed I-I. Plate 118 has an arm 118a attached thereto while rod 119a has a pin 119b extending therefrom and collar 1190 with coil spring 119d whose ends engage said plate and collar.

Plate 118 as shown in FIG. 18 is pivoted inwardly depressing control button 117a and is held in that position by arm 118a engaging pin l19b. An operator by manually pushing said plate can disengage arm 118 from pin 119b whereupon plate 118 will pivot out and move upwardly through spring 119d releasing control button 117a. Thus plate 118 can be held against control button 117a whenever the operator requires the same.

A double source of electrical current is indicated by double wall socket 120 with plugs 121 and 122 each plugged in one of the sockets. Plug 121 is connected to switch 35 while plug 122 is connected to the electric motor, clutch and brake 14 for energizing the same.

An air tube 123 is connected to a source of air under pressure (not shown) and to and through box 124, FIG. 3, which houses solenoid valves A, B, C, D and 140 and air speed regulators 125, 126 and 127 and tube 128, FIG. 14, connected to said tube 123.

Referring to FIG. showing the back of sewing machine 0, piston rod 31a, see FIG. 3, extends through bed H and is loosely connected to lever 129 pivoted on arm R by a pin 130. A pair of nuts 131 in threaded engagement with threads 132 of rod 31a are on each side of lever 129. Said lever 129 is pivotally connected by pin 133 to link 134 while link 134 is pivotally connected by pin 135 to the conventional presser foot raising and lowering lever 136 of the sewing machine.

Mounted on the top of the sewing machine 0, adjacent to the handwheel V is a bracket 137, having a downwardly extending leg 138. Secured to said leg 138, is an air cylinder 139 having a piston rod 141 extending therefrom in the direction of the handwheel V. A pin 142 pivotally supports arm 143 on said bracket so that ann 143 extends between leg 138 and handwheel V. The free end of arm 143 has a roller 144 rotatably mounted thereon which is adapted to move into notch 145 on the handwheel V when said piston rod 141 is extended due to air being forced into cylinder 139 through tube 166 which is connected to control valve 140. The notch 145 is located in such a position on handwheel V so that the needle bar 8 of the sewing machine will be in top dead center position when said roller 144 is engaged in notch 145.

Referring to FlG. 7a, notch 145 is in the periphery of a ring 146 held by setscrews 147 on handwheel V modified to receive the same. Housing 38 has an extension 148 integral therewith and link 149 attached to said extension. One end of spring 150 is attached to link 149 and its other end to arm 152 while stop 151 extends from extension 148 to arm 152 limiting the contraction of spring 150.

Screws 153 extend through openings 154 in bracket 137 into the top of said sewing machine for retaining said bracket thereon. Screw 155 extends through washer 156 and spring 157 into threaded opening 1550 in said bracket.

The threaded end of cylinder 139 has nut 158 and washer 159 thereon and extends into threaded opening 160 in said bracket for being supported thereby.

Setscrew 161 is in threaded opening 162 for engaging the end of pin 142 in opening 174 for retaining said pin therein.

Elbow 163 is in threaded engagement with threaded opening 164 in cylinder 139 while eyelet 165a and sleeve 165 are in said elbow and nut 164a is in threaded engagement with said elbow retaining tube 166 to said elbow.

Clamp 167 for wire 51 and arm 152 are attached to bracket leg 138 by screws 168 passing through openings 169 in arm 152 into threaded openings 169a in leg 138. Clamp 170 for wire 51 has screw 171 extending through washer 172, clamp 170 and into threaded opening 172a in arm 152.

Arm 143 has a lateral opening 173 through which extends pin 142 and a roller pin 175 extending through arm openings 176 and roller 144 rotatably retaining said roller partially in arm recess 174. A retaining ring 177 fits the end of roller pin 175 for holding the same in place.

FIG. 14 is a combination electrical and pneumatic schematic diagram showing the electrical as well as compressed air connections between the elements hereinbefore referred to. In this diagram there is also included relays R and R whose operation will be hereinafter described.

FIG. 16 is a view of the electrical circuit wiring diagram of FIG. 14 when needle T is in its up position and presser foot U raised, but with synchronizer valve 140 omitted. When the operator releases his heeling action on treadle F, the presser foot U will drop.

FIG. 17 is a view of the electrical circuit wiring diagram of FIG. 14 when needle T is in its down position.

In the operation of a sewing machine 0, modified according to the present invention, thread M is passed to post P, through guide Y, between disc 95c and disc 95d, through thread tension lever Z, through eye 75 and pigtails 80, between valve stem and seat 91, through the eye of needle T and doublelooped through bed X and opening 104 in tube 99. The thread from bobbin AA also passes through opening 104 in tube 99 and bed X so that the end of thread M and the bobbin thread are above bed X.

If the operator presses forward on the treadle F, the sewing machine will be operated in the normal manner. That is, pressing hard forwardly and down on said treadle causes the sewing machine to run at top speed while letting up on said treadle causes the sewing machine to slow down and taking the foot off the treadle completely stops the sewing machine stopping the sewing action.

When the operator feeds the workpiece across bed X beneath needle T and presser foot U and heels down on treadle F raising link 1 pressing link 4 against microswitches MS M and MS 02, FIG. 3, tripping said microswitches, microswitch MS 01 supplies current to points 45 and 50. Cam 40 rotates at the speed of the sewing machine and alternately opens and closes contacts 44 and 49 with points 45 and 50 respectively of the needle positioner. Contact 44 and point 45 control the up position of needle T while contact 49 and point 50 control the down position of needle T. By energizing point 45 and contact 44, the sewing machine will stop with needle T all the way up while energizing point 50 and contact 49, the sewing machine will stop with needle T all the way down. Thus if point 45 and contact 44 are energized, the sewing machine can be made to stop with needle T up, since cam 40 will open contact 44 from point 45 when said cam rotates around to that position breaking the electrical circuit.

lf contact 49 engages point 50 they will supply current to the solenoid valves D and 10 and relay R,. Said solenoid valves D and 10 pass compressed air to the positioning cylinder 24 by tube 25 and the brake cylinder 9 by tube 90 extending piston rod 23 which pulls cable 17 rotating pulley 16 in a direction which moves rollers 53 against teeth 56 of the slip clutch of FIGS. 8 and 9 against pulley 16 causing said clutch to grab and thus rotate shaft 14a rotating in transmitter 14 and also pulley 15, belt W and handwheel V causing cam 40 to rotate until it opens contact 49 from point 50. At the same time the needle positioner, solenoid valves and relay R are deenergized shifting piston rod 23 into cylinder 24 and putting brake cylinder 9 in its brake position stopping handwheel V, opening the contacts 44 and 49, thus the brake of transmitter 14 is released and reapplied very quickly while contact 49 and point 50 are open. Needle T is thus now positioned all the way down through the workpiece. Also at the same time when relay R, was deenergized the normally closed contacts in said relay supplied current to solenoid valve C passing air to cylinder 31 lifting presser foot S through rod 310, lever 129, links 134 and of FIG. 15, which allows the operator to turn the workpiece around the needle. Piston rod 23 returns into cylinder 24 through the slip action of the clutch in pulley 16.

Said slip clutch of pulley 16 is necessary to prevent the reverse rotation of the shaft of handwheel V which would cause needle T to come out of the workpiece and said slip clutch allows piston rod 23 to return into cylinder 24, its starting point, without reversing the rotation of handwheel V.

With the operator still heeling backwards on treadle F, be can push knee plate 118 against microswitch 117, closing the same and energizing contact 44 and point 45, solenoid valves D and 10 and relay R thus the brake of transmitter 14 is released and piston rod 23 pulls pulley l5 and the slip clutch of pulley 15 around so that needle T is moved up. The brake of transmitter 14 is then quickly reapplied and solenoid valves A and B actuated releasing disc 950 from disc 95d releasing thread M, moving pigtails 79 and 80 to the left of FIG. 5 drawing thread M in recess 63, raising piston rod 109 so that band 102 gives thread M and the bobbin thread a U-shaped bend as shown in FIG. 5 and then band 101 severs the threads from the workpiece automatically. With microswitch 117 set in the needle up position, current is sent directly to valve which will open allowing air to pass through tube 166 to cylinder 139. As the handwheel U is rotated by the positioning cylinder 24, roller 144 will ride on ring 146 until it engages notch 145 at which time the needle T will be in top dead center position in which position the normal thread tensions of the sewing machine are released to allow the thread M to be drawn freely from the supply by the thread puller. Presser foot U remains in its up position until the operator lets up on his heel on treadle F, at which time said presser foot drops. When piston rod 81 goes into cylinder 82 as far as allowed by screw 83, finger 70 activates microswitch 64 which energizes relay R breaking the return line of the synchronizer solenoid 140 to return it to its normal position. Relay R is locked in the down position by current from microswitch MS 02 and starts the return of piston rod 81 to its position in FIG. 5 and at the same time activates piston rod 109 and bands 101 and 102. When piston rod 81 reaches its position of FIG. 5 it operates microswitches 65 and 65a, and piston rod 109 is lowered. Releasing microswitch 117, the foot lift solenoid valve C is energized lifting presser foot U.

With the operator still pressing down with his heel on treadle F and holding microswitch 117 closed and then releasing said microswitch 117 before cam 40 reaches and opens contact 44, piston rod 23 will turn transmitter shaft 14a and pulley 15 around to the down position of needle T before said needle stops and presser foot U is raised. This puts one stitch in the workpiece at a time. Such operation requires a quick tap on knee plate 118 with the operators knee, while to cut the thread from the workpiece as hereinbefore described requires microswitch 117 to be held closed somewhat longer.

For greater speed in cutting the thread M from the workpiece, knee plate 118 can be locked against microswitch 117 by pushing said knee plate all the way down, see FIG. 18, rotating said knee plate against control button 117a and raising said knee plate so that the hook on arm 118a engages pin l19b. Then the operator can at any time heel backward on treadle F which activates piston rod 109 and thus bands 101 and 102, positioning the needle up, releases the tension on the thread, pulls the thread, trims the workpiece and raises the presser foot. As long as the treadle is heeled, the presser foot remains up permitting the removal of the finished work piece and the introduction of a new workpiece. However, said microswitch must be released and opened by manually moving arm 118a frompin 119b and said knee plate from control button 1170 before the needle T down-positioning elements as hereinbefore described can be operated.

When the operator presses forwardly or toes down hard on treadle F the sewing machine 0 operates in the normal manner at top speed. Letting up on treadle F causes the sewing machine to slow down and taking the foot off of the treadle F completely stops the sewing machine.

Lever 87 is positioned between valve stem 90 and block 68 so that movement of said block to the entire right of FIG. 5 pushes said valve stem to the right against spring 89 releasing the thread M. However, when block 68 is to the left of FIG. 5, spring 89 returns said valve stem against seat 91 against thread M. At any time the operator can manually pivot lever 87 to move either valve stem 90 or block 68 if desired.

Solenoid valves A, B, C, D and 10 are conventional electrically operated valves such as manufactured by the Automatic Switch Co., Florham Park, New Jersey, Catalog Nos. GY8314A33 and GY8314A51. Similarly regulators 125, 126, 29, 24a and 127 are conventional airflow control valves.

The present invention is capable of considerable modification and such changes thereto as come within the scope of the appended claims is deemed a part thereof.

We claim:

1. In a sewing machine having a reciprocating needle and bobbin, a thread cutoff comprising a fixed cylinder, a piston rod slideably extending from said cylinder, a pair of curved superposed tubes fixedly mounted on said cylinder and having ends positioned above said bobbin, a pair of bands fixedly connected to said piston rod and each slideably mounted in one of said tubes, one of said tube ends having a thread opening above the end of the other of said tubes, resilient means tending to retain said piston rod with said bands in said tubes and 

1. In a sewing machine having a reciprocating needle and bobbin, a thread cutoff comprising a fixed cylinder, a piston rod slideably extending from said cylinder, a pair of curved superposed tubes fixedly mounted on said cylinder and having ends positioned above said bobbin, a pair of bands fixedly connected to said piston rod and each slideably mounted in one of said tubes, one of said tube ends having a thread opening above the end of the other of said tubes, resilient means tending to retain said piston rod with said bands in said tubes and means for supplying compressed air to said cylinder for moving said piston rod against said resilient means and thus said bands from said tubes for cutting the threads at said tube ends. 